Aircraft often have an on-board auxiliary power unit to provide electrical power and compressed air to various systems. When the aircraft is on the ground, the auxiliary power unit is the primary source of power to drive the environmental control systems, hydraulic components, and the starters for the engines. During flight, the auxiliary power unit may provide pneumatic and electric power.
The auxiliary power unit is typically arranged within a fire containment enclosure in the tailcone of an aircraft. Generally, one or more intake ducts extend between respective intake openings in the exterior surface of the aircraft and the auxiliary power unit and/or the fire containment enclosure to define airflow passages through which air for the auxiliary power unit is drawn. The air flowing through the intake duct may be used to run the auxiliary power unit, cool the auxiliary power unit oil, and/or ventilate the auxiliary power unit compartment. It is generally desirable to improve the fire containment capabilities of the auxiliary power unit, particularly at the intake ducts extending between openings in the fire containment enclosure to the exterior of the aircraft.
Accordingly, it is desirable to provide auxiliary power unit assemblies with improved fire containment characteristics. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.